C64 Take Apart

Its finally come my post with the take apart of the Commodore 64. This is the C64C that I got off of Ebay. Its not as cool as the original breadbox one, but when I next have some money might just get my hands on one and do a take apart of it. The commodore is one of my favourite computers. For my dissertation I am working on creating on emulation of the sound chip of the C64 and this take apart will show that chip and the other parts that make up the C64 for all you techno geeks and cyberpunks out there. Before we start I must apologize for the glare in the pictures its just that I have a rubbish digital camera but I don't think it obstructs the picture so I have decided to continue with it.

On the side of the C64 we have to control ports used for connecting a joysticks or even a mouse that could be used with the GEOS operating system which was a GUI OS for the C64. We also have on the side a power switch and a din plug used for supplying power.

On the back of the machine starting from left to right we first have the cartridge slot that allows the C64 to be expanded and they also used make game cartridges. The switch next to this is used to select which TV channel is used. Next to the switch we have a DIN connector that allows the machine to output audio and a composite video signal. This connector also can also be used to input audio into the SID chip which is very important for my project. Next the AV DIN we have another DIN which is a serial port used to communicate with printers or disk drives. After the DIN we have a rectangular slot that is used to connect the commodore cassette unit to the machine. And the final connector on the back is a User Port connector that allows the C64 to communicate with various devices such as a VICMODEM. I currently have sourced connectors that fit this slot and am working on creating a PC64 cable and a RS232 cable. The creation of these will be next blog posts.

On the back of the machine we have screws that once are unscrewed we can then take off the top case. The top case has a power connector for the power LED's on the front of the case.
Underneath the keyboard we have a dusty cardboard electro magnetic shield used to protect the main electronic circuitry of the C64. The keyboard rests on 2 metal stands so the keyboard does not lay on the bottom case.

Once the keyboard is removed and the ribbon controller for the keyboard is disconnected and the main board is unscrewed from the bottom case we are left with this, the main “motherboard” of the C64.

The chip that is in the centre of this
picture is the SID chip. This little chip is a 3 voice synthesizer capable of 4 types of waveforms for each voice and was used for sound effects and music. If your curious about how this sounds go on over to the High Voltage SID collection and download the collection. To play the files you will need a suitable player such as Sidplay or if you are on OS X try Sidplay OS X. I would recommend listening to Rob Hubbard or Martin Galway's tunes as these guys are some of the best C64 composers if not the best? The SID in this machine is labelled as a 8580R5 which means that it is one of the newer chips.

To the left of the SID chip is a chip labelled 8565R2. This chip is the VIC-II. The version in my machine is a PAL version and is a HMOS-II version. The VIC is responsible for the graphics and sprites. Some SID tunes are also done on an interrupt caused by the VIC chip when it refreshes a certain pixel. This interrupt is called a raster interrupt. And when this happens calls the play routine for the SID tune.

The chip on the right that is labelled 6526A is used to communicate with serial ports such as the user port plug on the back of the machine and input from the keyboard. It is a CIA chip and also has a timer on board.

The image above is zoomed up from the SID chip so you can see on the left the 2 din connecters that were described earlier on the back of the machine. Next to the DIN connector we have a RF modulator that will mix audio and video signals by modulating them together so they can be output on a aerial lead for output to a television. Next to this we then have the cartridge expander port. Back in the day you could by cartridges that would fit onto here and could contain games or could even contain a Machine Code Monitor which would allow you to view memory locations and disassemble them or assemble commands at memory locations.

The chip in the centre of this picture which is labelled 8500 is the CPU of the C64. This chip has been manufactured using the HMOS process. The CPU is clocked at a speed 1Mhz and the official name of this CPU is the  6510. The 6510 uses the same instruction set as the 6502 but the only difference is the the 6510 has an 8bit general purpose input output port which was used to bank switch the memory mapped input output. In the C64 each chip is allocated an address on the address bus. But because the CPU can only access 16bits which means 65536 bytes this meant that the input output devices had to be mapped against memory locations. Because of this the 6510 CPU allows bank switching so as to switch a bank between memory or input output devices.

Well I hopped you enjoyed my short tour of the C64. As you can see the machine was quite an amazing machine and some people are still writing software and demos for this machine pushing it to the limits.

If you have the time or see anything wrong with this article please send me feedback on it so I can continually improve it. That’s it for now until next time ;)